This invention relates to a label switch network system or a policy server and particularly a label switch network system that realizes traffic engineering by intensively controlling various flows in the label switch network or a policy server used in the label switch network system.
In recent years, research and development on PBN (Policy Based Networking) and its application have been promoted with the aim of making IP (Internet Protocol) networks more sophisticated and simplifying its management and administration (Y. Nomura, et al., “Policy Based Networking Architecture for Enterprise Networks”, ICC' 99, 1999).
Also, the MPLS (Multi Protocol Label Switching) technique has been attracting attention. The technique has introduced a new concept, “a label”, for transferring IP packets and can perform IP level (layer 3: L3) routing by a switching process in lower layers (layer 2:L2) such as ATM (Asynchronous Transfer Mode), frame intermediate and Ethernet (Rosen, et al., “Multiprotocol Label Switching Architecture”, work in progress (IETF-Draft), 1999).
Especially, for label switch networks (hereinafter sometimes referred to as label networks), such as the MPLS network, it is crucial to realize traffic engineering including an optimal route set-up for every flow, load sharing and bypassing failures.
To provide service regarding traffic engineering, such as setting up optimal routes for every flow (setting up explicit routes in consideration of QoS (Quality of Service), and aggregates of IP flows), traffic load sharing and improving failure tolerance by setting up redundant links in the label switch networks, it is generally required to set up appropriate L2 paths by collecting information on the utilization conditions of the networks or to select L2 paths appropriate for transmitting IP traffic out of existing (already set up for a call) L2 paths. Here, a label network means an ATM network and L2 paths mean connections specified by such identifiers as VPI and VCI.
The abovementioned service of the past has been provided in the MPLS networks having a system configuration illustrated in FIG. 1. In the MPLS network, every node is a label switching router LSR having a layer 3 (IP level) router function. LSRs (from LSR1 to LSR5 in FIG. 1) basically have a function of selecting and setting up L2 paths utilized for communicating arbitrary IP flows and a function of setting up L2 paths leading from the ingress to the egress of the MPLS network by intermediateing control messages for setting up the L2 path between LSRs hop by hop. These control messages contain transmission quality parameters set at the ingress LSR and parameters that explicitly specify LSRs to be intermediateed.
In order to realize various services made available by MPLS, selecting appropriate L2 paths is a critical function. Since in the prior MPLS network distributed controls among LSRs are premised, it is necessary for one LSR to know the status of other LSRs using communications protocols among LSRs and not only to maintain and manage the status information but also to calculate appropriate L2 paths on the basis of such status information so that the LSR may select appropriate L2 paths in the whole MPLS network.
For the above purpose, each LSR needs to perform a protocol process for distributing and collecting the status information, maintain and manage the status information of other LSRs and calculate L2 paths.
In the distributed control method where the status information is exchanged with adjacent LSRs hop by hop, processing time in proportion to the number of hops among LSRs is required until the whole network receives the status information.
In addition, the redundant link service cannot switch paths quickly when a failure arises in a working path, unless spare paths were set in the MPLS networks beforehand. Therefore it is necessary to set aside bandwidth for the spare paths beforehand. However the secured resources (including bandwidth for spare paths) cannot be utilized in normal use, thus lowering the resource utilization efficiency.
Also, the conventional MPLS network directly deals with mapping (matching) of IP flows and LSP (Label Switched Path), it is necessary to switch lines at LSRs as many times as the number of the IP flows when the lines need to be switched and thus managing cost and processing cost utilizing thereof becomes high.
The results of the above is that in a conventional MPLS network wherein the distributed control method is employed, to realize the above various services, not only the cost and processing time inevitably increase but also efficiency of resource utilization becomes low.